Electrical generators are used in a wide variety of applications. Typically, an electrical generator operates in a stand-by mode wherein the electrical power provided by a utility is monitored such that if the commercial electrical power from the utility fails or is otherwise interrupted for a certain period of time, the engine of the electrical generator is started, either automatically or manually by a customer, causing the electrical generator to supply emergency or backup electrical power. More particularly, the engine drives an alternator to provide electrical current to power selected electrical loads (“electrical circuits”) that are connected to the electrical generator, which is typically through a dedicated electrical panel, i.e., a transfer panel.
When the electrical power generated by the alternator reaches a predetermined voltage and frequency desired by the customer, the transfer switch transfers the load imposed by the customer from the commercial power lines to the electrical generator. The electrical generator then supplies electrical power to selected loads, which are typically deemed to be critical loads, such as HVAC equipment, refrigerator(s), lighting, sump pumps, well pumps, and, if applicable, medical equipment.
The 2008 edition of the United States National Electrical Code (NEC 2008) required an increase in the ratio of rated generator output to maximum possible loading on the electrical generator. Thus, to meet the NEC stated supply/load requirements, larger electrical generators than previously needed are now required or the generator-connected loads must be limited. Larger electrical generators are generally more costly in acquisition and operating costs, have a larger physical footprint, and are noisier. It is often desirable to hide or otherwise soften the appearance of the electrical generator, such as when used to provide emergency or backup power to a home. Similarly, many homeowners' associations have noise emission requirements that ultimately limit the size of electrical generator that can be used. So, in general, there is a demand for physically smaller electrical generators. However, reducing the physical size of the electrical generator typically also results in a reduction in the rated power output of the electrical generator, which can place a limit on the number of electrical loads that are fed by the electrical generator during utility power interruption. Many users, however, prefer to power as many electrical loads as possible even when utility power is unavailable. With NEC 2008, the number of generator-connectable loads is further limited.
One of the challenges faced by engineers in designing smaller electrical generators without sacrificing power output is preventing overloading of the electrical generator when it is being used to supply electrical power to the generator-connected loads during utility power interruption or failure. One solution has required an electrician to hardwire only those loads, through the transfer panel, that the electrical generator is capable of supporting. Thus, for this traditional wired approach, if the electrical generator was sized to supply 200 Amps of output, for example, the total amperage draw of the electrical loads connected to the electrical generator through the transfer panel would be limited to approximately 200 Amps. NEC 2008 allows consumers to have their power usage monitored, such as for thirty days, with recordings for peak power usage. This data can then be used to select an appropriately sized generator. However, this process is typically expensive and will often result in the consumer needing or wanting a larger sized generator.
Another type of solution is the use of a control module, such as that described in U.S. Publication No. 2007/0222295, which adds and sheds loads based on the demand placed on the electrical generator. With this microprocessor-based model, if a given load is turned off or is otherwise not loading the electrical generator, the control module adds a load on the electrical generator. Similarly, if the current draw of the online loads exceeds the rated output of the electrical generator, or some other value representative of an overload condition, the control module provides command signals to one or more remotely controllable switches to shed (“electrically disconnect”) one or more electrical loads until the loading on the electrical generator is matched to or below the rated output of the electrical generator. The plurality of loads are typically prioritized which sets an order by which the loads are added or shed, i.e., remotely controllable switches are switched. In this regard, if a new load is added to the loads to be powered by the electrical generator, the loads must be re-prioritized. This re-prioritization typically requires an electrician to rewire how the loads are connected to the transfer panel or change the association of the remotely controllable switches and the loads so that the control module connects and disconnects the loads in the right order.